CoC Oral Exam Preparation (Part – 20): EKG
How does emergency alarm ring?
Ans: Continuous ringing of bell. Emergency situation is explained at the muster situation. Pattern of Emergency signal is indicated on Muster list
Q. Explain the Fire Tube and Water Tube Boiler.
Fire Tube Type: Due to simple design of the tubes effective heat transfer takes place, but periodical cleaning/maintenance is slightly difficult. Soot blowing is not effective for regular cleaning. Used with low pressure boiler
Water Tube type: In comparison to fire tube type heat transfer is not so so effective. Gas side cleaning is easier, sometimes fixed water spray design is used for cleaning. Soot blowing is effective , used with medium – high pressure boiler
Q. What is Ogee ring?
Ans: Connects the bottom of the furnace to the boiler shell plating.
Q. How the boiler Gas side is cleaned during operation?
i. By means of steam, soot blowing
ii. By injecting soot remover powder (chemical) to the system.
Sketch a gauge glass and explain blow down procedure.
Ans: a) Close steam and water cock, open drain cock, nothing should come out the cocks are not leaking.
- Open and close steam cock to check cock is clear.
- Open and close water cock to check cock is clear.
- Close the drain
- Now open water cock, water should gradually rise up the top of gage glass.
- Open the steam cock, the water should fall to the level of the water in the boiler.
What is the consequence of low water level? What is your immediate action?
Ans: Boiler running without water will cause overheating the tubes, tube plates and shell, that will lead the boiler to face thermal over stress damage, crack or rupture to the tube, tube plates, shell plates.
However, low water level alarm should be activated and boiler firing will shutdown. If the boiler water level found minimum at the water cock level it is safe to put feed water in the boiler. If the level is below this line care has to be exercised not to thermally stress boiler while putting water into boiler.
What is the consequence of high water level? What is your action?
Ans: This will cause priming of the boiler, loss of heat from the heaters, possibly loss of steam pressure.
As per as possible steam heating to be minimized temporarily, carry out partial blow down to normal level. Then introduce normal heating again.
What is the purpose of treating boiler water?
a) Prevent scale formation
b) Prevent corrosion
c) Control of sludge formation and prevent carry over to the system
d) Prevent entry of foreign matters to the boiler.
What type of chemicals are used to treat low pressure boilers?
Lime Ca(OH)2 and soda ash are used Na2CO3 are used to deal with calcium and magnesium compounds in the boiler water.
MgCl2 + Ca(OH)2 Mg(OH)2 + CaCl2
CaCl2 + Na2CO3 CaCO3 + 2 NaCl
What is the problem if boiler water contaminated with oil?
i) Create layer on the boiler plates, tubes etc and reduces heat transfer and thermal stresses are induced.
ii) initiates corrosion
With regard to capacity state the regulation for steering gear?
Ans: A vessel at deepest draught and at maximum service speed should be able to move rudder angel from 350 one side and to 350 other side. It should be capable to move 350 one side to 300 other side within 28 seconds.
The auxiliary steering gear should be able to move from 150 one side to 150 other side at half service speed or 7 knots whichever is greater in 60 seconds.
Describe steering gears routine checks before departure and arrival ports.
I) After prolonged use of auto pilot check remote/manual steering on arrival.
ii) Check both steering gear power unit on arrival, run simultaneously on maneuvering channel.
On departure from port within 12 hours:
- Check main and auxiliary steering gear
- Remote control system for steering gear
- Steering position on navigation Bridge
- Emergency power supply
- check compass rudder angel position
- Auto isolation arrangements
How often the emergency steering drill is carried out? How you used to carry out in your last ship?
Ans: Every three months.
Controlling the pumps in either direction by means of manual push buttons from steering gear room locally.
What is the function of by pass valve and relief valves?
Ans: By pass valve are used to open circuit any particular unit.
Relief valves are given to relief over pressure, especially during rough sea undue movements of rudder created extra oil pressure which is relieved by them to avoid any rupture, leakage, damage.
Care and management of pumping systems:
Candidates should remain aware of various pumps working principle.
Q: Classify pumps.
Ans: i) Positive displacement pumps e.g. reciprocating, screw, gear etc.
ii) Rotor dynamic e.g. Centrifugal,
Q: A centrifugal pump not taking suction, what action you are going to take?
- Check valves open
- Suction live have crack/leakage
- Air Ingress to check, primer to check
- Suction line jointing to check
- check suction filter clogged
- should the above not complying check the wear ring clearance excessive
- may be the impeller securing arrangement detached.
Q: Why positive displacement pumps require relief valves?
Ans: with the pumping action, pumping rate is same but if the delivery is obstructed the pressure will be built up gradually, which will damage line, casing etc. To protect from above relief valves are required to be fitted.
Q: What type of pump is used for Oily Water SWeparator? Is centrifugal pump is suitable for the above?
Ans: positive displacement pumps e.g. rotor line screw, reciprocating and gear pumps are used for the above. Centrifugal pumps are not suitable for above because they produce large quantities of small oil droplets.
Q: How the tubular coolers thermal expansion is allowed?
Ans: i) By means of expansion piece
ii) by means of free end arrangements
Q: What for “bilge injection” v/v is used? What is relevant regulation?
Ans: Bilge injection valve is used for in case of serious flooding in the machinery space. Diameter of the valve should be 2/3rd of the diameter of main sea inlet, valve spindle should be clear of engine platform.
What is the function of oil sensing probe in OWS?
Ans: The Capacitance probe in 1st stage senses and causes the solenoid to be energized through control switch. Hence control air access to the diaphragm controlled piston valve to drain oil to bilge oil tank.
Q: what is the function of coalesce filter ?
Ans: Removes fine solids up to certain extent. Small drops of oil coalesce to form larger drops. These rise up to oil collecting space.
Q: How to ensure no accidental discharge O/B will take place from O.W separator?
Ans: i) 15 PPM alarm monitor will activate and discharge P/P will stop automatically.
ii) Three way valve will activate on reaching effluent content 15 PPM, will divert the flow to bilge water tank instead of O/B.
Construction, maintenance and operation of fire fighting equipment, fire detection and prevention:
Candidate should know the basic principle operation of portable extinguishers, fixed fire fighting installations and fire detector sensors.
Q: With regard to capacity state the regulation for emergency fire p/p.
Ans: Capacity should be at least 40% of fire pumps but not less than 25m3/hour. To
supply 2 jets 13 mm dia with a horizontal throw of 13 m.
Q: How does smoke detector works? How do you test it ?
Ans: smoke is sensed by the photo electric call, this signal is transmitted to trigger the
alarm. It can be tested by (i) Smoke (ii) Spray can
Q: How does sprinkler system work? Where is it used ?
Ans: Sprinkler heads are fitted with quartzoid bulb. Heat expands the liquid and
shatters the bulb. Water strikes a deflector to ensure a cover of floor area of 12m2. On dropping system pressure sprinkler P/P starts automatically.
Used for accommodation, alleyways of passenger ships and some cargo spaces.
Q: What is international shore connection?
Ans: It is to be provided to enable water to be supplied from another ship or from shore
to the fire main.
PCD 132 mm, Outer dia of flange 178 mm, Bore (inner dia of flange) 64 mm.
4 bolts are required of 16 mm dia and 50 mm length.
Q: With regard to CO2 total flooding state the regulation?
Ans: 85%of the gas must be released within two minutes. The quantity of gas carried
- must be sufficient to give a free gas volume equal to 40% of the volume of the space except where the horizontal casing area is less than 40% of the general area of the space.
- Must give a free gas volume equal to 35% of the entire space whichever is greater.
Q: How the CO2 total flooding system is maintained?
Ans: CO2 room visual inspection is carried out regularly (say weekly), CO2 alarm checked on monthly basis and servicing and others checking of the system is carried out annually by authorized work shop.
Modern vessels maintain routine check lists of weekly, monthly, quarterly, 6 monthly and annually.
Q: What is fireman outfit?
a) A safety lamp
b) A fireman’s axe
c) A breathing apparatus or ii. Smoke helmet, or A smoke mask.
Q: Before wearing a BA set, what would you check?
i) Pressure normal; 140-210 bar
ii) Test alarm whistle working
iii) Check mask “seals”, not leaking
Alarm comes when air contents are brought about 80%.
Q: State the procedure of CO2 flooding
Ans: On completion of assessment , permission granted by Master in consulting with chief engineer to carry out flooding:
- personnel counted
- all openings sealed including flaps, ducts for ventilation
- shut down all fans, blowers, pumps, purifiers, motors by remote stop device
- shut down fuel supply by quick closing valve operation
- follow operating instruction for operating pilot cylinder for gang release and there after the master valve
- use boundary cooling and observe fire and rescue procedure.
Q: what are the safety incorporated in co2 system? How it works?
Ans: 1) relief v/v on manifold, rupture dick for cylinders
11) interlock for fan, pump and purifiers stop
111) audio-visual alarm while operating lever box is opened.
iv) overriding procedure for releasing, if pilot release fails
co2 cylinders are stored to maintain temp below 55ºc and at 52 bar. If pressure rise above 177 bar at temp 63ºc or above, rupture disk on cylinders opens. This gas is released through safety v/v on manifold.
When the co2 cyl require recharging? How the content be checked?
Re-charge when weight reduce by 10%
- check by weighting, or radio active level indicator or ultrasonic gauging.
Codes of safety working practices:
Candidates should be familiar with a book “code of safe working practices” available on board
vessels. It is important to identify safeties to encounter hazards.
Q: What precaution should be taken while entering a enclosed space?
Ans: To be complied with company check lists but in the general it will cover followings:
- Assessment of atmosphere
- Illumination (safety)
- Permit to work
- Self contained B/A set stand by
- Ladder required as appropriate
- Man standby at entry position
- Communication should be established
Q: What precaution should be taken before decarbonizing a M/E unit?
Ans: Company policies are relevant. In general they are
- Immobilization granted
- Turning gear engaged
- Starting air valve shut off
- System, staring air line vented
- Starting air distributor inlet valve shut
- Appropriate notices given
- Fuel, cooling etc relevant valves in appropriate position
- Over head crane tested.
Methods of manicuring, including bridge control Systems and Variable pitch propellers.
Bridge Control Procedures:
Engine should be tested from ECR first to ensure safe operation. If satisfactory, control is change over to bridge and engine tested ahead and astern, telegraphic printer checked working Properly.
Bridge alarm panel checked, in order. During maneuvering speed program may be cancelled, while at full away condition load up program should remain on to speed up gradually. Maximum rpm can be limited from ECR.
Variable pitch Propellers:
While testing engine/vessel ahead and astern movements, only propeller pitches are adjusted to get desired movements. Engine need not to stop for ahead/astern moves. Engine clutch/declutch mechanism can be utilized as appropriate. Hydro oil level, pressure, and pumps should be checked.
Pitch control – tried out from bridge/control room as well from local control.
Q: With respect to M/E , what is emergency control?
Ans: Should M/E remote operation is not working, it may be operated from emergency / local control stand which will cover following:
- Manual Fuel Control
- Manual Air control
- Manual Reversing
Q: What action you are going to take in the event of a black out/M/E failure?
- Inform bridge/chief engineer
- Engineers alarm may be raised for additional help
- Emergency lighting/emergency generator will be active
- identify the problem, preferably start other generator which was not in service and restore power.
- Run appropriate cooling P/Ps, reset all needful breakers, start all other plants
- Prepare M/E and restore same after informing bridge
- Check all Standby machineries and emergency equipments at ready mode.
Working principle and constructional details of a compressor, air receivers, and associated equipment:
Candidates should have understand the efficacy of inter coolers, P-V diagrams gain in efficiency.
Q: What is the working principle of a main air compressor?
Ans: Reciprocating motions are used to in conjunction with spring loaded non -return suction and delivery valves to achieve compressed air. Intercoolers are used to acquire gain in efficiency.
Q: Describe the construction of a main air compressor you used in our last ship.
Ans: It was a in line reciprocating 2 stage compressor. 1st stage piston relatively larger and 2nd stage piston smaller in comparison, materials respectively aluminum and cast iron. Both stages were having spring loaded suction and discharge non-return valves. Inter stage cooler and after coolers were there.
Q: Other than in line, what different type of compressor is used?
Ans: Tandem type compressor are the other type commonly used. 1st stage piston relatively larger, 2nd stage piston exists on top of above relatively of smaller size.
Q: Why the bumping clearance is important?
Ans: Bumping clearance should be optimum. The more clearance volume increase, volumetric efficiency and hence capacity decreases.
Q: How do you take bumping clearance?
Ans: Remove suction or disch valve assy from the unit, place a small ball of lead wire on the piston edge. Then rotate the flywheel by hand and to take the piston at TDC. Remove and measure the thickness of lead wire ball.
Q: What is function of intercooler and after cooler?
Intercooler: i) Decreases air temp
ii) Reduces work done
iii) Maintains safe lubrications
iv) Increase compressor efficiency
After-cooler: i) Separate oil and water from compressed air
ii) Reduces air temperature before the filling receiver
Q: What mounted safeties are incorporated with a main air compressor?
Ans: i) Relief valves are fitted at the discharge of each stage
ii) incorporated discharge non return valve
iii) Bursting discharges are fitted with intercoolers to protect from over pressure due to tube leakage
iv) Un-loader/drain valves
Q: What safeties are incorporated for compressor protection?
i) Low pressure alarm, stop for lube oil
ii) Jacket high temperature/air discharge high temperature, alarm, stop.
Q: Describe the special features for main air receivers?
i) Manhole door elliptical, for the ease of opening and consider strength of the pressure vessel
ii) Circumferential and longitudinal welding seams are existing.
iii) Relief valve fitted (if isolated from relief valve, fitted with fusible plug, melting point 1500 C.)
iv) Drain valve, pressure gauge
v ) Pressure switch for cut in /cut off air compressor auto running.
Operations, Testing Power, the running adjustment to maintain performance:
Candidates should know how to use indicator machine, taking power cards, draw cards etc and
know how to measure engine power.
Q: If an individual unit of M/E shows high exht temp, what should you do ?
Ans: i) If the parameter goes beyond limit, that case engine power/rpm may have to be reduced informing bridge and chief engineer. Need to find out fault.
ii) check the funnel smoke and check the pyrometer is correct, fuel rack in order.
iii) Fuel injection equipment, – fuel valve, fuel P/P may be faulty. Take power card to understand fuel injection, all units peak pressure may be compared
iv) Compression pressure can be checked from above, to have an idea about liner wear/piston rings.
v) Exhaust valve operation can be checked visually (through glass) or light spring card can be taken to ensure the problem with exhaust valve or not.
vi) check particular unit scavenge drain line
vii) Should all above are in order, consider mistiming for late injection or mistiming of early opening.
Q: M/E all units exhaust temps are high what could be the reason?
Consider it is a common problem for all, hence it can be of followings:
- Faulty governor or fuel linkage
- Fuel quality to be assessed
- Problem with T/C, scavenging not enough
- T/C Air filter dirty
- Scav. Air temperature high
- Residual temperature low, responsible for incorrect injection
- check fuel load, if the vessel at shallow water
- Ships hull fouled
- in worst case due bad quality fuel injection equipment may be worn.
Q: How do you calculate POWER in a conventional method?
Ans: – take power card (in-phase diagram)
Where: PmLAN in KW = POWER ……………… (1)
Pm = MEAN EFFECTIVE PRESSURE , L= STROKE LENGTH, A= AREA OF PISTON , N= REVS NO.
Calculate area of the diagram by using planimeter, check length of diagram
Calculate the mean height of diagram, which is n = area (mm²)/ length(mm)
Now the MEP= h (mean height, mm) x spring scale (bar/mm)
i.e MEP found in bar or, MEP is (barx10²) kN/m²
from (1) we get power= PmLAN kW for one cylinder. For total engine, the result of other cylinders to be accounted for.
Q: What was the main Engine Type in your last ship? How did you calculate engine power?
Ans: Engine Type SULZER5RTA48T
Power of first estimation was P1(KW) can be read from the graph read by (Fn-F0)×N from
Where Fn = Load indicator pos
F0 = 1.22 (mean), pos of load indicate pos corresponding to FO P/P idle stroke
N = Engine speed (rpm)
Effective Power N = P1×—————-×————- KW
r = Specific gravity of FO at engine inlet temp
r`= 8.18.7 kg/m3 FO used during trial (at engine inlet temperature)
Hu= Lower catorific value of fuel oil
Hu`= 42.50MJ/Kg (lower cal. Value of DO used during trial)
Safe and efficient operation and maintenance of marine diesel Engine
candidates should remain aware of the working principles of various main and auxiliary machineries. Should know how to decarb a particular 2 stroke/4 stroke engine unit and relevant inspections. To be familiar with operation recommended by the manufacturer, specially while during operation with defective components.
What is the indication of black/blue smoke?
Ans: Black smoke indicate incorrect /incomplete combustion. Blue smoke indicates burning of LO with the combustion. Smoke should be clear.
What are the causes of scavenge fire?
i) Blow past through liner and piston rings
ii) Due to incorrect fuel injection
iii) Due to lack of cooling, breaking of Cylinder LO film
iv) Excessive cylinder lubrication give undue fuel and cylinder film breakage will cause hot gas to blow by, consequence scavenge fire.
What action you are going to take with above?
i) Inform bridge/chief engineer officer
ii) Slow down engine to extinguish fire
iii) Scavenge drain can be checked carefully
iv) shut off fuel to the particular unit
v) Increase cyl lubrication to give adequate sealing
vi) check funnel, scav drain, scav temp if satisfactorily return to normal with appropriate rpm.
vii) if above are not successful, not extinguished, stop engine, engage turning gear, mask T/C air filter, use fixed CO2 / steam to extinguish.
viii) On completion, inspect, rectify the fault then start engine.
Candidates to know starting air explosion and c/case explosion, causes, remedy and action.
What inspection is carried out on piston ring?
i) Axial clearance .
ii) Butt clearance
iii) Ring thickness
iv) Radial thickness
v) ring tension
What inspection should carry out with cylinder liners?
i) Check the ridge on top, remove by grinding if any
- ii) check for crack, oilyness
iii) Check lubricators, condition of retaining Cylinder LO
iv) Check for wear (gauging), ovaliti
vi) Abrasive wear
What is thrust block?
Ans: This makes use of the engine bedplate and seatings to distribute the propeller thrust to the ships structure.
What is the function of flywheel?
Ans: i) Store energy while acceleration and releases while deceleration, smooths out fluctuation of engine speed.
- ii) Turns the engine for maintenance
iii) Used as pointer of engine position
What are the TBN values for C/C oil of cross head engines and trunk piston engine?
Ans: Engine using residual fuel, C/C oil to be alkaline.
For X-head engine 10-15 TBN
For trunk piston engines up to 40 TBN
What is microbial degradation?
Ans: It is a infection of C/Case oil by micro organism. This live by consuming hydrocarbons in the base oil together with nitrogen, sulpher and phosphorus from additives. Cooling water etc. leakage are responsible for depleting the above situation.
Safeties during working shipboard electrical system:
Electrical shock and fire can cause loss of life and damage to the equipment, hence in general
following should be complied :
- To be familiar with ship electrical equipment and diagram.
- Operate as makers instructions
- Maintain as per makers instruction
- Guards, covers, doors etc securely tightened
- While shutting off the power, inform duty officer/engineer of the watch
- While maintenance being done, remove fuse etc.
- Before working with the equipment confirm circuit is dead.
- Do not leave live conductors or rotating parts exposed
- Avoid overloading equipment
- Use appropriate warning notices
What are the conditions of electric shock?
- Minimum 15 mA AC or DC current is enough to cause an electric shock. Circuit may be from hand to hand or hand to foot. Shock current is related to the applied voltage and body resistance. Unfortunately if the applied voltage goes up, body resistance goes down, that means shock current is further increased.
What are the safety of the panel boards?
- Insulated barriers
- Some panel board cannot be opened unless the breaker is off
- Adjacent floor covered by insulated mats.
During a watch you find low insulation resistance alarm, what is your action?
Ans: Inform chief engineer officer and electrical engineer officer. Meanwhile take following actions to find detect the faulty equipment.
- Isolate/change the running motor and check megger
- If not found, check galley, laundry equipments
- Deck crane electrical motor
- Fwd/aft electrical equipments
After the faulty equipment is isolated, insulation indicator will restore back to normal.
How do you check insulation resistance?
i) Phase to phase
ii) Phase to earth.
In dry dock while connecting shore electrical power, what will you check?
Ans: i) Check supplied voltage
iii) Phase sequence ( specially check at least one E/R exhaust fan that it is rotating in normal direction).
iv) If shore supply is earthed neutral, the ships body has to be earthed.
v) Check the capacity of the circuit breaker.
What is the sequence method synchronizing ? if synchroscope and light methods are out of order how do you parallel generator?
Ans: Two lights bright and one light goes out (dark), synchronizing method is sequence method.
Same phase of the bus bar and incoming generator are connected across a 500 V voltmeter. When voltmeter indicates 0 to maximum slowly and when voltmeter shows at zero, breaker to be closed. This is the point where they are in correct phase sequence.